丙烷氧化脱氢VMgO催化剂活性位的研究

应用低温ＥＰＲ等方法对比研究了浸渍法和硝酸盐法制备的两个系列ＶＭｇＯ催化剂的活性位．结果表明,只有在合适的制备条件下,生成了适量Ｖ４＋离子的钒酸镁物相才具有较好的催化活性,含有适量Ｖ４＋离子的正、焦钒酸镁可能是丙烷氧化脱氢制丙烯ＶＭｇＯ催化剂的活性相．含有Ｖ４＋的Ｍｇ３Ｖ２Ｏ８活性相的表面活性位结构可能为Ｖ４＋－Ｏ－Ｍｇ－Ｏ－Ｖ５＋,含有Ｖ４＋的α－Ｍｇ２Ｖ２Ｏ７活性相的表面活性位结构可能为Ｖ４＋－Ｏ－Ｖ５＋．     

Fe2O3—K2O催化剂上乙苯脱氢反应动力学

Fe_2O_3-K_2O双组份催化剂在反应温度580～640℃,液体空速0.5～2.5h~(-1),水/乙苯(体积比)1～3范围内乙苯脱氧反应动力学数据。列出主副反应单位或双位吸附的各种反应类型,用线性回归分析法进行判别以确定反应模型和估算各参数值,进一步用数值积分法优化计算不同温度下的反应速度率常数,吸附系数,频率因子和活化能。结果表明:双组份催化剂活性高,但苯乙烯选择性差,副产物苯和甲苯同时从平行反应和联串反应产生,其中大部份来自联串反应,主副反应均用双位吸附单分子反应模型较为合适。     

乙醇水溶液可见光催化脱氢的研究

考察了光催化剂浓度、粒径、反应温度、乙醇浓度和高温热处理对悬浮Pd/CdS粉末光催化剂的乙醇水溶液可见光催化脱氢活性的影响,得出2.5m gml~(-1)为最佳催化剂浓度,活性达300ml/h·l;温度在305～365K内,反应的表观活化能为36.6kJmol~(-1);在乙醇浓度低于50％时,脱氢反应对乙醇是一级反应;实验证明高温热处理使Pd颗粒向内表面扩散,且强化Pd移去CdS表面的自由电子,两者均提高脱氢活性;得到选择性高于70％的主要氧化产物乙醛;提出了可能的反应机理。     

铜锌催化剂的活性及对甲醇吸附的研究

以二氧化硅为载体的浸渍型铜锌催化剂对甲醇脱氢具有较高的活性和选择性。Zno的加入能降低CuO的还原温度，同时对甲醇的吸附量增加，提高了催化剂的选择性，实验表明，催化剂的活性位是零价铜，Zno只起助催化剂的作用。     

燃烧条件对乙苯脱氢催化剂相结构和耐湿性的影响

采用XRD和冷水浸泡或后煮沸的方法分别研究乙苯脱氢催化剂的相结构和耐湿性,表明催化剂耐湿性的改善取决于K_2Fe_(22)O_(34)相的存在,而只有在高于900℃的温度下煅烧才能大量生成K_2Fe_(22)O_(34),但它与催化活性似乎并无直接关系。     

在Fe_2O_3－K_2O催化剂上乙苯程序升温脱附研究──探讨乙苯脱氢反应机理

乙苯在Ｆｅ＿２Ｏ＿３－Ｋ＿２Ｏ催化剂上的ＴＰＤ研究表明，新鲜催化剂表面有α和β两种活性位，均具脱氢、脱乙基和裂解活性．乙苯吸附后能脱氢生成苯乙烯和脱乙基生成苯，若预先吸附水亦可脱甲基生成甲苯，新鲜催化剂表面氧化能力较强，脱下的的氢或烷基会立即与表面晶格氧作用生成Ｈ＿２Ｏ和ＣＯ＿２，并致使催化剂表面被还原产生新的γ活性位．γ位裂解性能较强，但在吸附水后也具有脱氢和脱烷基活性，水对甲苯的生成起着重要的作用，α活性位可能是Ｋ＿２Ｆｅ＿２Ｏ＿４相，β和γ位可能是Ｆｅ＿２Ｏ＿３和Ｆｅ＿３Ｏ＿４（部分还原的氧化铁）相．     

Preparation and catalytic effect of porous Co3O4 on the hydrogen storage properties of a Li-B-N-H system

A porous Co_3O_4 with a particle size of 1–3 μm was successfully prepared by heating Co-based metal organic frameworks MOF-74(Co) up to 500 °C in air atmospheric conditions. The as-prepared porous Co_3O_4 significantly reduced the dehydrogenation temperatures of the LiBH_4-2LiNH_2 system and improved the purity of the released hydrogen. The LiBH_4-2LiNH_2-0.05/3Co_3O_4 sample started to release hydrogen at 140 °C and released hydrogen levels of approximately 9.7 wt% at 225 °C. The end temperature for hydrogen release was lowered by 125 °C relative to that of the pristine sample. Structural analyses revealed that the as-prepared porous Co_3O_4 is in-situ reduced to metallic Co, which functions as an active catalyst, reducing the kinetic barriers and lowering the dehydrogenation temperatures of the LiBH_4-2LiNH_2 system. More importantly, the porous Co_3O_4-containing sample exhibited partially improved reversibility for hydrogen storage in the LiBH_4-2LiNH_2 system.     

Catalytic effect of a novel MgC_(0.5)Co_3 compound on the dehydrogenation of MgH_2

The application of magnesium hydride(MgH_2) is limited due to the high reaction temperature and slow kinetics during dehydrogenation. In order to ameliorate the dehydrogenation property of MgH_2, MgC_(0.5)Co_3 compound with induction and catalytic effects was introduced into the Mg/MgH_2 system via ball-milling and hydriding combustion methods in present study. Compared to the pure MgH_2,the initial hydrogen desorption temperature of MgH_2–MgC_(0.5)Co_3 composite lowered to 237°C, decreasing by 141°C. At 325°C the MgH_2–MgC_(0.5)Co_3 composite could release 4.38 wt% H_2 within 60 min, which is 4.5 times the capacity of hydrogen released by as milled-MgH_2. Besides, the hydrogen desorption activation energy of the MgH_2–MgC_(0.5)Co_3 composite was dramatically reduced to 126.7 ± 1.4 k J/mol. It was observed that MgC_(0.5)Co_3 was chemically stable and no chemical transformation occurred after cycling, which not only inhibited the nucleation and growth of composite particles, but also had a positive effect on the hydrogen desorption reaction of MgH_2 due to its catalytic effect.This study may provide references for designing and synthesizing Mg–C–Co alloy compound for the Mg-based hydrogen storage area.     

TPR-TPO技术研究甲醇直接脱氢铜基催化剂

TPR-TPO是一种表征负载或非负载的金属或金属氧化物催化剂的高灵敏度技术,用此技术研究甲醇直接俄氢制无水甲醛负载型铜基催化剂Cu/SiO_2和Cu-Cr/SiO_2,动力学活性评价表明Cu-Cr/SiO_2的活性和单程寿命明显优于Cu/SiO_2,XPS和TPR-TPO谱测定,以及催化剂的再生实验结果表明,Cu的还原以及表面积炭是活性下降的主要原因,在高温条件下,铬组份可能以铬酸铜形式存在,使部分铜难还原,并阻碍了铜微晶的聚集。     

小型乙苯脱氢装置操作条件的考察

在自行设计的小型乙苯脱氢装置上，对过程的适宜操作条件及苯乙烯的分析方法进行了考察。结果表明，在反应温度田０～６００℃；液空速０．８ｈ￣（－１）及Ｈ＿２Ｏ／乙苯为１．５（质量比）的条件下，乙苯单程转化率为４７％～６１％，选择性达到９２％～９３％，这一结果与工业装置的实际生产数据相当吻合。因此，可利用该小型装置对工业生产的操作条件进行模拟。苯乙烯含量的色谱分析与折光指数分析对比显示。两者相当接近，故可采用相对较为简单的折光指数法测定乙苯脱氢反应液相产物中苯乙烯的含量。